U.S. Pat. No. 7,082,910 discloses an internal combustion engine, namely, a two-stroke engine, which has a channel for supplying a mixture as well as a separate channel for supplying air. The air channel opens at the cylinder bore and is connected to a transfer channel in the region of top dead center of the piston. Scavenging advance air is stored in advance in the transfer channel.
It has been shown that in scavenging advance engines of this kind, the scavenging of the combustion chamber does not take place only with pure air but that the mixture can also reach the combustion chamber during the scavenging operation which then escapes through the outlet. This situation deteriorates the exhaust-gas values of the internal combustion engine.